1. Field of the Invention
The present invention relates to the field of voltage control devices. In particular, the invention is concerned with a voltage control apparatus using a transformer with a plurality of secondary output connections coupled with electromechanical relays controlled by a control circuit in order to provide a selected output voltage to a load.
2. Description of the Prior Art
One of the typical design assumptions for motor-driven equipment is that the line voltage supplied to the load such as a motor will be in a certain range. However, local conditions may result in line voltages outside the range for which the equipment was designed. Such can occur because of brownout conditions, inadequate supply capacity, and other loads on a supply circuit. High voltage conditions may also occur because of inadequate line regulation.
Both high and low voltage conditions can contribute to poor performance of the equipment and can even result in motor burnouts and the like. Such can be especially problematic for critical applications such as cryogenic preservation equipment.